1. Field of the Invention
The present invention relates to a liquid crystal dispensing apparatus, and particularly, to a liquid crystal dispensing apparatus that has a simple structure and that can drop liquid crystal at an exact position on a substrate.
2. Discussion of the Related Art
Recently, various portable electric devices such as mobile phones, personal digital assistants (PDA), and notebook computers have been developed, and therefore, needs for a flat panel display device for use in a small, light and power-efficient device are correspondingly increasing. To meet the needs, flat panel display devices such as liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and vacuum fluorescent displays (VFD) have been actively researched. Of these flat panel display devices, the LCD is highlighted due to current mass production, easiness in a driving scheme, and realization of superior image quality.
The LCD is a device for displaying information on a screen using refractive anisotropy of liquid crystal. As shown in FIG. 1, the LCD 1 comprises a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 formed between the lower substrate 5 and the upper substrate 3. The lower substrate 5 is a driving device array substrate. A plurality of pixels (not shown) are formed on the lower substrate 5, and a driving device such as a thin film transistor (TFT) is formed on each pixel. The upper substrate 3 is a color filter substrate, and a color filter layer for reproducing real color is formed thereon. Further, a pixel electrode and a common electrode are formed on the lower substrate 5 and the upper substrate 3 respectively. An alignment layer is formed on the lower substrate 5 and the upper substrate 3 to align liquid crystal molecules of the liquid crystal layer 7 uniformly.
The lower substrate 5 and the upper substrate 3 are attached by a sealing material 9, and the liquid crystal layer 7 is formed therebetween. In addition, the liquid crystal molecules are reoriented by the driving device formed on the lower substrate 5 to control the amount of light transmitting through the liquid crystal layer, thereby displaying information.
Fabrication processes for a LCD device can be divided into a driving device array substrate process for forming the driving device on the lower substrate 5, a color filter substrate process for forming the color filter on the upper substrate 3, and a cell process. These processes will be described with reference to FIG. 2 as follows.
Initially, a plurality of gate lines and data lines are formed on the lower substrate 5 to define a pixel area by the driving device array process and the thin film transistor connected to both the gate line and the data line is formed on the each pixel area (S101). Also, a pixel electrode, which is connected to the thin film transistor to drive the liquid crystal layer according to a signal applied through the thin film transistor, is formed by the driving device array process. R (Red), G (Green), and B (Blue) color filter layers for reproducing the color and a common electrode are formed on the upper substrate 3 by the color filter process (S104). In addition, the alignment layer is formed on the lower substrate 5 and the upper substrate 3 respectively, and then the alignment layer is rubbed to induce surface anchoring (that is, a pretilt angle and alignment direction) for the liquid crystal molecules of the liquid crystal layer between the lower substrate 5 and the upper substrate 3 (S102 and S105). Thereafter, a spacer for maintaining the cell gap constant and uniform is dispersed onto the lower substrate 5. Then, the sealing material is applied onto outer portion of the upper substrate 3 to attach the lower substrate 5 and the upper substrate 3 by compression (S103, S106, and S107).
On the other hand, the lower substrate 5 and the upper substrate 3 are made from a glass substrate of larger area. That is, the large glass substrate includes a plurality of unit panel areas on which the driving device such as TFT and the color filter layer are formed. To fabricate the individual liquid crystal display unit panel, the assembled glass substrates should be cut into unit panels (S108). Thereafter, the liquid crystal is injected into the empty individual liquid crystal display unit panel through a liquid crystal injection opening (S109). The filled liquid crystal display unit panel is completed by sealing the liquid crystal injection opening, and each liquid crystal display unit panel is inspected, thereby completing the LCD device (S109 and S110).
As described above, the liquid crystal is injected through the liquid crystal injection opening. The injection of the liquid crystal is induced by a pressure difference. FIG. 3 shows a device for injecting the liquid crystal into the liquid crystal display panel. As shown in FIG. 3, a container 12 in which the liquid crystal is contained is placed in a vacuum chamber 10, and the liquid crystal display panel is located on an upper side of the container 12. The vacuum chamber 10 is connected to a vacuum pump to maintain a predetermined vacuum state. Further, a liquid crystal display panel moving device (not shown) is installed in the vacuum chamber 10 to move the liquid crystal display panel from the upper side of the container 12 to the surface of the liquid crystal to contact an injection opening 16 of the liquid crystal display panel 1 with the liquid crystal 14 (this method is called as liquid crystal dipping injection method).
When the vacuum degree within the chamber 10 is decreased by inflowing nitrogen gas (N2) into the vacuum chamber 10 in the state that the injection opening of the liquid crystal display panel 1 contacts with the liquid crystal, the liquid crystal 14 is injected into the panel through the injection opening by the pressure difference between the pressure in the liquid crystal display panel and the pressure in the vacuum chamber. After the liquid crystal is entirely filled into the panel 1, the injection opening 16 is sealed by a sealing material to seal the liquid crystal layer (this method is called as vacuum injection method of liquid crystal).
However, there are several some problems in the liquid crystal dipping injection method and/or vacuum injection method as follows.
First, time for the liquid crystal injection into the panel 1 is increased. Generally, a gap thickness between the driving device array substrate and the color filter substrate in the liquid crystal display panel is very narrow as order of magnitude of micrometers, and therefore, a very small amount of liquid crystal is injected into the liquid crystal display panel per unit time. For example, it takes about 8 hours to inject the liquid crystal completely in fabrication process of the 15 inches-liquid crystal display panel 15, the liquid crystal fabrication process time is increased due to the liquid crystal injection of long time, thereby decreasing fabricating efficiency.
Second, the liquid crystal consumption is increased in the above liquid crystal injection method. A small amount of liquid crystal out of the liquid crystal contained in the container 12 is injected into the liquid crystal display panel 10. On the other hand, when the liquid crystal is exposed to atmosphere or to a certain gas, the liquid crystal is contaminated by reaction with the gas. Therefore, the remaining the liquid crystal should be discarded after the injection when the liquid crystal 14 contained in the container 12 is injected into a plurality of liquid crystal display panels 10, thereby increasing the liquid crystal display panel fabrication cost.